Screw



UNITED STATESv PATENT OFFICE.

HAYVVARD A. HARVEY, OF ORANGE, ASSIGNOR TO HARVEY SOREIV COMPANY, OF JERSEY CITY, NEW JERSEY.

SCREW.

SPECIFICATION forming part of Letters Patent No. 248,164, dated October 11, 1881.

' Application filed June 22, 1881. (No model.) A

To all lwhom 'it may concern:

Be it known thatI, HAYWARD A. HARVEY, of Orange, New Jersey, have invented a certain Improvement in Rolled Screw-Nails, of which the following isa specification.

My improvement, which relates to the shape in cross section of the thread of a.rolled screw-nail, is especially intended for application to the screw-nailshown and described in Letters Patent ot' the United States N o. 221,729, granted to me November 18, 1879.

Screw-nails, or screws which are intended for insertion by driving, ure provided preferably with ratchet-threads. Itis desirable that l the edges of the threads shall project transversely outward beyond the body of the shank of the blank, and to this end I employ in the formation of the thread the mechanism shown and described in Letters Patentot the United States No. 223,730, granted to me January 20, 1880, for. an improvement in machines for rolling threads of screws or bolts.

By the use of this mechanism the threads are formed partly by abrasion and partly by thedisplacement of the metal and its rearrangement in the form of a lib extending spirally aroundthe body of' the blank.

I have found that by making the longer side ot' the thread-that is, the side toward the point of'the screw-nail-concave, which, as will be obvious, is effected by making the. ribs ot' the dies correspondingly convex, the metal displaced by the impress of the die iows more easily outward, and the rolled thread not only acquires a sharp edge,- but its edge is thrown farther-outward from the body of the blank.

The side of the thread toward the head of the screw-nail maybe a spiral plane, which in cross-section is at,'or nearly at, a right angle with the axis otv the screw or, it' desired,

it may be slightly concave in cross-section. In either case the concavity ofthe under side of the thread, or, in other words, the corresponding convexity of the rib lor die which impresses that part of the thread, is the principal factor in inducing the outward tlow ot' the metal, and the complete filling ot' the depressions in the die, and thus the foundation ot a sharp-edged projecting thread.

In the accompanying drawings, representing rolled screw-nails containing myimprovement, Figure 1 is an elevation ofA a ratchetthreaded screw-nail, showing the threaded portion of the body in central longitudinal section. Fig. .2 is a similar representation of a screw-nail, illustrating the application ot my improvement to those forms ot ratchetthreads in which the upper side of the thread is either outwardly and downwardly inclined or is slightly lconcave in cross-section.

For the purposes of the present case either ol' the forms of thread illustrated in the drawings may be called ratchet-threads,7 the distin guishing characteristic of the class of threads to which my invention applies being that their lower sides form a more acute ar.- gle lwith the side ot' the body than their upper sides.

It will be seen on referenceto the drawings that the heads A of the screw-nails are provided with the projections or nipplesa a, which are intended to receive theimpact of the hammer by which the screw-nail is driven into an object, and whichVA serve to engage the screwdriver employed to withdraw the screw-nail.

The body B is provided with a projecting spiral thread, b, the distinguishing characteristie of which is that its under side, C, is concave in cross-section.

The upper side, D, of the thread may, in cross-section, occupy a plane at right angles to the axis of the screw-nail, as shown in Fig. l, or the thread may be provided with an outwardly and downwardly inclined upper face, E, as shown in the upper portion of the body in Fig. 2, or the thread may be provided with a concave upper face, F, as shown in the lower portion ot' the body in Fig. 2. In either case it will be seen that the edges G ot' each convolution of the thread have such an outward projection that the diameter, measuring from the edge of the thread on one side to a point in line with the edges ofthe thread on the other side, is consid erably greater than the diameter of the shank A ofthe blank.

Driven screw-nails are held in position by the swelling or springing ot' the woodinto the depressions in the periphery ot1 the body, and it has heretofore been proposed to turn down the upper pait of the shank of a Wood-screw A rolled screw-nail provided with a sharp- 1o to make room for such .swelling or springing edged thread projecting beyond the Unthreadof the wood. ed portion of the body7 one or both sides of I do not therefore claim, broadly, a screw the thread beingr ooneavein cross-section, subi 5 having the Unthreaded portion of its shank of stantially as set forth.

less diameter than the diameter of a cylinder H. A. HARVEY. capable ot' containing` the threaded portion of Vitnesses: the body; but M. L. ADAMS,

That I do eiaiin as my invention iS GEO. W. MIATT. 

